attribute.

:param info_name: the info name for this invocation.  Generally this
                  is the most descriptive name for the script or
                  command.  For the toplevel script it's usually
                  the name of the script, for commands below it's
                  the name of the command.
:param args: the arguments to parse as list of strings.
:param parent: the parent context if available.
:param extra: extra keyword arguments forwarded to the context
              constructor.

.. versionchanged:: 8.0
    Added the :attr:`context_class` attribute.
r